1. Technical Field
This invention relates to hybrid storage media and management of data stored thereon. More specifically, the invention relates to designating a first class of data to be retained on the non-volatile RAM (NVRAM) section of the storage media and a second class of data to be flushed from the NVRAM section to the physical data storage section of the hybrid storage media.
2. Description of the Prior Art
Non-volatile memory is computer memory that can retain stored information when power is not delivered to the memory. In a computer system, non-volatile memory is commonly found in the form of a hard disk, a floppy disk, or a flash drive. A hard disk is a magnetic disk on which a computer stores digitally encoded data. In general, a hard drive is a form of non-volatile memory that can retain stored information with or without power. Non-volatile memory may also be found in random access memory (RAM) and is known in the art as non-volatile random access memory (NVRAM). There are different types of NVRAM, including DRAM, SRAM, and flash memory. DRAM (dynamic random access memory) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since capacitors leak charge, the information eventually fades unless the capacitor charge is periodically refreshed. SRAM (static random access memory) is a type of semiconductor memory that used bi-stable laching circuitry to store each bit. Data is eventually lost when the memory is not powered over a period of time. DRAM and SRAM both require power in order to maintain their data over an extended period of time. Flash memory is another form of non-volatile memory that can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives. More specifically, flash memory is a specific type of EEPROM (electrically erasable programmable read-only memory) that is erased and programmed in large blocks. Accordingly, non-volatile memory can be found in various forms that support retention of data without delivery of power.
As noted above, hard disk drives are known in the art of computer systems to store data. A hybrid hard disk drive (HHD) is a hard disk drive with a buffer that uses NVRAM to cache data and a physical drive for permanent storage of data, hereinafter referred to as a physical drive. It is known in the art for the operating system to load data from the flash memory first when booting. This accomplishes at least two elements, speeding up boot time and reducing power consumption by removing the need to quickly spin up the drive. Depending on the caching protocol of the HHD, it is known in the art to flush data from the buffer to the physical drive. The physical drive will only need to spin up when the buffer nears its capacity or when the data required from the hard drive is not already stored in the buffer. Since the HHD utilizes NVRAM as opposed to RAM, the buffer is able to retain data in the event of power failure.
It is known in the art that all HHDs flush all of the data from the buffer to the physical drive. Different caching protocols are employed to dictate how and when the flush occurs. In the prior art, it is not possible to designate data that should be retained exclusively in the buffer and not subject to flushing to the physical drive. However, it is desirable in limited circumstances to retain specific data in the buffer without flushing such data to the physical drive. Accordingly, there is a need for an interface that retains designated data in the buffer, while allowing non-designated data to be flushed from the buffer to the physical drive.